Just minutes after the magnitude 7.4 Landers earthquake last Sunday, an unexpected "surge of seismic activity," mainly very small earthquakes, began 250 miles away in the Long Valley Caldera near Mammoth Lakes, according to a report by the U.S. Geological Survey. The increase in what scientists often call "sympathetic" minor quakes continued all the way up the eastern side of the Sierra Nevada and into the Cascade range around Lassen Peak and Mt. Shasta. Mt.

Earthquake experts Monday proposed establishment of a dense array of 250 Global Positioning System stations in urban areas of Southern California to allow more precise determinations of seismic strains accumulating in the region and improve long-range earthquake forecasting. Representatives of the Southern California Earthquake Center at USC, the U.S.

A 4.8-magnitude earthquake shook Baja Mexico at 10:33 a.m. Saturday, according to the U.S. Geological Survey. The quake was located 71 miles east of Tijuana and 22 miles south-southwest of Seeley, Calif. The quake was felt as far north as San Diego but there were no reports of damage there, authorities said. The quake was one of a cluster of four seismic events located very close to one another just south of the border, according to the USGS. The first was a magnitude 4.9 quake that occurred at 10:30 a.m.; the second was the 4.8 magnitude quake at 10:33 a.m.; the third was a 1.9 magnitude quake at 10:52 a.m. and the fourth was a 3.6 magnitude quake at 10:59 a.m.

Did you feel it? Then how do you feel about talking about it? Seismologists studying earthquake intensity now know that Southern Californians feel good about discussing the shaking they endured in Sunday's temblor near Palm Springs. By midafternoon Monday, nearly 27,000 people had filled out computerized questionnaires for the United States Geological Survey detailing their personal reactions to the magnitude 5.2 quake. The 8:41 a.m. shaker was initially pegged at magnitude 5.

Residents living on the U.S.-Mexico border were shaken Sunday by a magnitude 4.6 earthquake, part of a cluster of moderate aftershocks stemming from the magnitude 7.2 quake that jolted Baja California a week ago, authorities said. Sunday's quake struck at 9:42 a.m. and was centered about 29 miles south southeast of Mexicali, the U.S. Geological Survey said. No damage or injuries have been reported. In a 19-hour period from about 5 p.m. Saturday through noon Sunday, automated seismographs registered at least 17 quakes of magnitude 3 or above with epicenters near Calexico or Mexicali, said Don Blakeman, a geophysicist at the USGS's National Earthquake Information Center in Golden, Colo.

Residents of Calexico in the Imperial Valley were jolted awake as a 3.1-magnitude earthquake struck at 4:12 a.m. Monday. Lights flickered and some light poles swayed as the aftershock struck the California border town. There were no immediate reports of injuries or property damage. The quake was centered about 34 miles south-southwest of Calexico, according to the U.S . Geological Survey. At the Best Western motel, patrons said it felt as if a large truck had backed into the outside wall, shaking furniture inside the rooms.

Ever since hundreds of earthquakes began rippling through southeastern California over the weekend, many asked the question: Could this be a precursor to the Big One? The answer: Probably not - at least, if this swarm of quakes follows past patterns. Certainly, the weekend's quakes were troubling for Imperial County, which is located in one of California's most earthquake prone regions. More than 400 earthquakes have been detected since Saturday evening, according to the U.S. Geological Survey.

More than two dozen earthquakes struck Monday night near the U.S-Mexico border in San Diego County, rocking a large swath of Southern California, prompting a momentary shutdown of the San Diego Padres game but causing no apparent major damage, officials said. The largest of the quakes — a 5.7 magnitude temblor — was recorded at 9:26 p.m, the U.S. Geological Survey said. It could be felt throughout Los Angeles County. That quake was centered five miles southeast of Ocotillo in San Diego County and 16 miles east-northeast of Jacumba in eastern San Diego County, the survey agency said.

Some called it an "earthquake cluster," others a "swarm. " Seismologists used the term "earthquake sequence. " Whatever the name, a series of more than 30 small to moderate temblors jolted Southern California on Tuesday night and Wednesday morning, rattling nerves but causing no significant damage. The cluster of earthquakes that struck near Yorba Linda was centered near the Whittier fault, but preliminary data suggested that fault was not responsible for the temblor, said Doug Given, a geophysicist with theU.S.

"Volcano Cowboys" is an extraordinarily intriguing look, by Dick Thompson, a veteran Time magazine reporter, at how volcanologists from the U.S. Geological Survey and a few other scientists outside the Survey coped with three of the world's major volcanic emergencies of the past 20 years. The eruptions of Mt. St. Helens in Washington state in 1980 and of Mt.